Toilet seat- how do I fix the small black burnt spot?

They are inexpensive to replace. Repair depends on construction of the toilet seat. Plastic? You could use sandpaper then rubbing compound working down to a polishing compound. If you don't have these things they will cost more than a new seat. If your seat is of compressed sawdust you can sand the burnt spot off then prime and repaint the entire seat. Again, more expensive than $10 replacement. Solid wood seats were popular for a while and are $35 and up for a replacement. Sand it off and try to match the stain then spray polyurethane over the entire seat.

really? take a 20 dollar bill out of you r wallet and buy a new one. there really is no excuse to reuse something like this - and this is more sanitary too.

If it is wood you can sand, patch hole if any, then repaint with enamel.

you could try an emery board, small piece of sandpaper to sand away the black spot, then seal with clear nail polish? I think you will always know it's there but your eye won't be drawn to it. Otherwise toilet seats are under $20 if you can swing that...

Toilet seats are not really that expensive, I would suggest a new one as a fix will only last for so long before you have to fix it again. I guess you can consider me too lazy on this one :)

replace seat .. not worthy to fix